Eimeria praecox infection ameliorates effects of Eimeria maxima infection in chickens.

The effect of Eimeria praecox on concurrent Eimeria maxima infection was studied in susceptible chickens. Cinical signs of coccidiosis were assessed in single E. praecox or E. maxima infections and compared to dual infection with both Eimeria species. Groups infected solely with 104 E. maxima oocysts displayed weight gains that were 48% of weight gain in uninfected controls. Weight gain in chickens infected only with 104 E. praecox oocysts was 90% of uninfected controls. Average weight gain in chickens infected with both E. maxima and E. praecox was 79% of controls, and showed no significant difference (P>0.05) from weight gain in E. praecox-infected chickens. Feed utilization (feed conversion ratio, FCR) in chickens infected with both species showed no significant difference (P>0.05) from FCR in non-infected controls or chickens infected with E. praecox alone; all showing a significant difference (P<0.05) from FCR in chickens infected solely with E. maxima. Although E. praecox did not appear to have a negative effect on weight gain and FCR, it did cause a significant decrease in serum carotenoids. Analysis of oocysts excreted by chickens during dual infection showed little effect of E. praecox on E. maxima oocyst production.